fix race caused by consecutive stun packets

src/switch_rtp.c

@@ -1127,7 +1127,7 @@ static void handle_ice(switch_rtp_t *rtp_session, switch_rtp_ice_t *ice, void *d
 						if (!strcmp(ice->ice_params->cands[i][ice->proto].con_addr, host) && 
 							!strcmp(ice->ice_params->cands[i][ice->proto].cand_type, "relay")) {
 
-							if (elapsed != 0 && elapsed < 5000) {
+							if (rtp_session->last_stun && elapsed < 5000) {
 								switch_log_printf(SWITCH_CHANNEL_SESSION_LOG(rtp_session->session), SWITCH_LOG_WARNING,
 												  "Skiping RELAY stun/%s/dtls port change from %s:%u to %s:%u\n", is_rtcp ? "rtcp" : "rtp", 
 												  host2, port2,